Combustion apparatus

ABSTRACT

A combustion apparatus has: a combustion housing; a partition plate provided in the combustion housing to partition a space in the combustion housing into a combustion chamber and an air supply chamber; and a plurality of rich-lean burners arranged in a right-left direction of the combustion chamber. A multiplicity of distributed holes are formed in the partition plate through which distributed holes secondary air is supplied from the air supply chamber to the combustion chamber. A flame rod facing to an upper side of a part of the rich-lean burners stops combustion when the flame rod does not detect any flames owing to a flame lift at a time of an oxygen deficiency. A supply quantity of the secondary air to the part of the rich-lean burners to which part the flame rod faces is larger than those to other parts.

BACKGROUND OF THE INVENTION

This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2010-127852, filed Jun. 3, 2010, which is incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a combustion apparatus equipped with a rich-lean burner and a flame rod for combustion stopping at the time of an oxygen deficiency.

DESCRIPTION OF THE RELATED ART

The following combustion apparatus has conventionally been known (see, for example, Japanese Patent Application Laid-Open Publication No. 2006-266516). That is, the combustion apparatus includes a combustion housing and a partition plate provided in the combustion housing to partition the space in the combustion housing into a combustion chamber and an air supply chamber on the lower side of the combustion chamber. The combustion apparatus further includes a plurality of rich-lean burners arranged in the right-left direction of the combustion chamber, and the combustion apparatus is configured to supply secondary air from the air supply chamber to the combustion chamber through a multiplicity of distributed holes formed in the partition plate. Incidentally, each of the rich-lean burners includes a lean flame port and a couple of rich flame ports, each provided at the upper end of the burner main body elongated in the front-rear direction thereof. The lean flame port jets out a lean mixture gas of a fuel concentration leaner than a theoretical air fuel ratio, and the rich flame ports are situated on both the sides of the lean flame port in the right-left direction thereof to jet out a rich mixture gas of a fuel concentration richer than that of the lean mixture gas.

Moreover, in such combustion apparatuses, the following combustion apparatus has also known (see, for example, Japanese Patent Application Laid-Open Publication No. 2009-162442). That is, the combustion apparatus is configured to be provided with a flame rod to face on the upper part of a part of the rich-lean burners, and to stop combustion when the flame rod enters a state of not detecting any flames owing to a flame lift at the time of an oxygen deficiency.

By the way, at the time of the oxygen deficiency, the primary air becomes insufficient, and the flame lift arises in a state in which the jet-out velocities of the mixture gasses become faster than their combustion velocities. In particular, in the rich-lean burner, the lean flame formed on the lean flame port lifts earlier than the rich flames formed on the rich flame ports. In this case, because the flame rod detects the flames until the rich flames also lift, the combustion of the burner does not stop. Then, the flame lifts owing to the oxygen deficiency sometimes advance in a part in which no flame rod is provided owing to the distribution unevenness of a mixture gas and the like to bring about an incomplete combustion.

SUMMARY

In view of the problem mentioned above, it is an advantage of the present invention to provide a combustion apparatus using rich-lean burners and being capable of surely stopping combustion before the worsening of combustibility owing to an oxygen deficiency.

In order to attain the object mentioned above, an aspect of the present invention is a combustion apparatus, comprising: a combustion housing; a partition plate provided in the combustion housing to partition a space in the combustion housing into a combustion chamber and an air supply chamber on a lower side of the combustion chamber; a plurality of rich-lean burners arranged in a right-left direction of the combustion chamber, each of the rich-lean burners including a burner main body elongated in a front-rear direction thereof, a lean flame port jetting out a lean mixture gas of a fuel concentration leaner than a theoretical air fuel ratio, and a couple of rich flame ports situated on both sides of the lean flame port in a right-left direction thereof to jet out a rich mixture gas of a fuel concentration richer than that of the lean mixture gas, the lean flame port and the rich flame ports being situated at an upper end of the burner main body; a multiplicity of distributed holes formed in the partition plate through which distributed holes secondary air is supplied from the air supply chamber to the combustion chamber; a flame rod facing to an upper side of a part of the rich-lean burners to stop combustion when the flame rod does not detect any flames owing to a flame lift at a time of an oxygen deficiency; wherein a supply quantity of the secondary air to the part of the rich-lean burners to which part the flame rod faces is larger than those to other parts.

Rich flames formed on the rich flame ports spread out to the outer sides to seek the secondary air at the time of an oxygen deficiency, here. Then, if the supply quantity of the secondary air is large, the rich flames are turned up from the outer sides by the secondary air blowing up to the outer sides of the rich flames. The rich flame ports on the outer sides in the burner main body are, furthermore, cooled by the secondary air, and the combustion velocity becomes slower. Consequently, the lifts of the rich flames become easier.

According to the present invention, the supply quantity of the secondary air to the part of the rich-lean burners to which part the flame rod faces is made to be larger than those to the other parts, and consequently not only the lean flame but also the rich flames lift at the initial stage of an oxygen deficiency in the installation part of the flame rod. The flame rod then falls in a state of not detecting any flames. Consequently, combustion can surely be stopped before the worsening of combustibility owing to the oxygen deficiency.

Now, it is also possible to provide a duct to lead the air in the air supply chamber to the part of the rich-lean burners to which part the flame rod faces for making the supply quantity of the part of the rich-lean burners to which part the flame rod faces larger than those to the other parts. However, this configuration needs the duct to increase the number of parts and to bring about an increase in cost.

Accordingly, in another aspect of the invention, it is preferable that the distributed holes in a part of the partition plate through which part the secondary air to flow to the part of the rich-lean burners to which part the flame rod faces passes are formed to have an opening area of the distributed holes per unit area of the partition plate larger than those of other parts. The supply quantity of the secondary air to the part of the rich-lean burners to which part the flame rod faces can hereby be made to be larger than those to the other parts without using any ducts, and the configuration is advantageous in order to decrease the number of parts to achieve the reduction of cost.

Advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention, in which drawings:

FIG. 1 is a plan view of the combustion apparatus of an embodiment of the present invention;

FIG. 2 is a sectional view taken along the line II-II in FIG. 1;

FIG. 3A is a view showing a combustion state of a rich-lean burner at the time of the normal state thereof;

FIG. 3B is a view showing a combustion state of the rich-lean burner at the time of a slight oxygen deficiency; and

FIG. 3C is a view showing a combustion state of the rich-lean burner at the time of a slight oxygen deficiency in a flame rod setting part.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention will be explained with reference to the drawings.

With reference to FIGS. 1 and 2, the combustion apparatus of the present embodiment includes a combustion housing 1. The upper surface of the combustion housing 1 is opened, and a heating object (not illustrated) such as a heat exchanger is placed on the combustion housing 1.

A partition plate 4 partitioning the space in the combustion housing 1 into a combustion chamber 2 and an air supply chamber 3 on the lower side of the combustion chamber 2 is provided in the combustion housing 1. A combustion fan (not illustrated) is connected to the bottom face of the air supply chamber 3 with a duct 5 put between them, and air is supplied from the combustion fan to the air supply chamber 3. A multiplicity of distributed holes 4 a are formed in the partition plate 4 at the positions corresponding to the arrangement pitch portions of rich-lean burners 6, which will be described later. Then, the combustion apparatus is configured in order to supply the air supplied to the air supply chamber 3 into the combustion chamber 2 as secondary air through the distributed holes 4 a.

The plurality of rich-lean burners 6, each being elongated in the front-rear direction thereof, is arranged in the right-left direction of the combustion chamber 2. As shown in FIGS. 3A, 3B, and 3C, each of the rich-lean burners 6 includes a lean flame port 62 and a couple of rich flame ports 63 at the upper end of the burner main body 61 elongated in the front-rear direction thereof. The lean flame port 62 jets out a lean mixture gas of a fuel concentration leaner than a theoretical air fuel ratio. The rich flame ports 63 are situated on both the sides of the lean flame port 62 in the right-left direction thereof and jet out rich mixture gases of a fuel concentration richer than that of the lean mixture gas. The rich-lean burner 6 further includes rectifying plates 62 a installed in the lean flame port 62 and back flow regions 62 b provided on both the sides of the lean flame port 62 between the lean flame port 62 and the rich flame ports 63, the back flow regions 62 b jetting out no mixture gases therefrom. Moreover, with reference to FIG. 2, the burner main body 61 is provided with an inflow port 64 for the lean mixture gas and an inflow port 65 for the rich mixture gas, both formed at the front end of the burner main body 61 on the lower part thereof. The inflow port 65 is formed on the upper side of the inflow port 64. The burner main body 61 is further provided on the upper end thereof with bridge portions 66 dividing each of the lean flame port 62 and the rich flame ports 63 into a plurality of divisions in the front and rear direction of the burner main body 61. Incidentally, the fuel concentration of the rich mixture gas is generally set to be richer than the theoretical air fuel ratio, but it is also possible to set the fuel concentration to be slightly leaner than the theoretical air fuel ratio.

Moreover, a rising portion 41 is formed by bending the front edge of the partition plate 4, and a manifold 7 is installed on the front side of the rising portion 41 so as to obstruct the front surface of the combustion housing 1 at the lower part thereof. The manifold 7 is provided with gas nozzles 71 and 72 for the lean mixture gas and the rich mixture gas, respectively, to be opposed to the inflow ports 64 and 65, respectively, of each of the rich-lean burners 6. Then, the combustion apparatus is configured in such a way that a fuel gas is supplied from each of the gas nozzles 71 and 72 to each of the inflow ports 64 and 65, respectively, and that the primary air is supplied from the air supply chamber 3 to each of the inflow ports 64 and 65 through a vacant space formed between the rising portion 41 and the manifold 7.

A damper plate 42, in which openings corresponding to the inflow ports 64 and 65, respectively, of each of the rich-lean burners 6 are formed, is provided on the front surface of the rising portion 41. Then, the opening of the damper plate 42 corresponding to the inflow port 64 for the lean mixture gas is formed to be larger to increase the supply quantity of the primary air to the inflow port 64 to generate the lean mixture gas. On the other hand, the opening of the damper plate 42 corresponding to the inflow port 65 for the rich mixture gas is formed to be smaller to decrease the supply quantity of the primary air to the inflow port 65 to generate the rich mixture gas.

On the front surface of the combustion housing 1 there are installed an ignition plug 8 and a flame rod 9. The flame rod 9 is arranged to face on the upper part of a part of the rich-lean burners 6. To put it concretely, the flame rod 9 is provided to face on the upper parts of the front end parts of a fifth and a sixth rich-lean burners 6 from the right side in FIG. 1. Then, when the flame rod 9 enters a state in which the flame rod 9 does not detect any flames owing to flame lifts at the time of an oxygen deficiency, that is, when a flame electric current flowing between the flame rod 9 and the burner main body 61 through a flame lowers to be a predetermined threshold value or less owing to the flame lift to an upper part higher than the flame rod 9, then the combustion apparatus is configured to close a solenoid valve (not illustrated) provided to be inserted in a gas supply route on the upper stream of the manifold 7 to stop the combustion.

As shown in FIG. 3A, here, at the time of normal combustion, a lean flame Fa is formed by the lean mixture gas jetted out from the lean flame port 62, and rich flames Fb are formed by the combustion of the rich mixture gases jetted out from the rich flame ports 63 by using the superfluous air in the lean mixture gas and the air from the distributed holes 4 a as the secondary air. At the time of a slight oxygen deficiency, as shown in FIG. 3B, the lean flame Fa lifts, and the rich flames Fb spread out to the outer sides to seek the secondary air owing to a decrease of the superfluous air in the lean mixture gas, but the lifts of the rich flames Fb are not brought about so much. If the state remains as it is, the flame rod 9 detects the rich flames Fb, and the combustion cannot be stopped at the initial stage of the oxygen deficiency.

Accordingly, in the present embodiment, the distributed holes 4 a in the part of the partition plate 4 through which part the secondary air to flow to the part of the rich-lean burners 6 to which the flame rod 9 faces passes are formed to be in a higher density than those in the other parts, and the opening area of the distributed holes 4 a per unit area of the partition plate 4 is made to be wider than those of the other parts. In the present embodiment, the flame rod 9 is installed in a position anterior to that of the rising portion 41 at the front edge of the partition plate 4, and the secondary air that has passed through the anterior region of the partition plate 4 detours from the upper end of the rising portion 41 to the front thereof to flow to the part of the rich-lean burners 6 to which the flame rod 9 faces. Accordingly, the distributed holes 4 a are formed to be in a high density in the front part (a part indicated by a letter A in FIGS. 1 and 2) of the partition plate 4 in a predetermined right-left direction range centering around the installation position of the flame rod 9. Incidentally, it is also possible to enlarge the distributed holes 4 a to be formed in the aforesaid part A of the partition plate 4 to enlarge the opening area of the distributed holes 4 a per unit area of the partition plate 4.

Hereby, the supply quantity of the secondary air to the parts of the rich-lean burners 6 to which the flame rod 9 faces becomes larger than those of the other parts. Then, if the supply quantity of the secondary air is large, as shown in FIG. 3C, the rich flames Fb are turned up from the outer sides by the secondary air blowing up to the outer sides of the rich flames Fb. Furthermore, the rich flame ports 63 on the outer sides of the burner main body 61 are cooled by the secondary air and the combustion velocity becomes slower. Consequently, the lifts of the rich flames Fb become easily arise.

Consequently, not only the lean flame Fa but also the rich flames Fb lift at the initial stage of an oxygen deficiency in the installation part of the flame rod 9, and the flame rod 9 falls in not detecting any flames. As a result, the combustion can surely be stopped before the combustibility worsens owing to the oxygen deficiency.

In the above, although the embodiment of the present invention has been described with reference to the attached drawings, the present invention is not limited to the embodiment. For example, it is also possible to provide a duct leading air in the air supply chamber 3 to the parts of the rich-lean burners 6 to which parts the flame rod 9 faces to increase the supply quantity of the secondary air to the parts of the rich-lean burners 6 to which parts the flame rod 9 faces to be larger than those of the other parts. However, this configuration needs the duct, and the number of parts increases to bring about an increase in cost. On the other hand, according to the embodiment described above, the supply quantity of the secondary air to the parts of the rich-lean burners 6 to which parts the flame rod 9 faces can be made to be larger than those to the other parts only by the setting of the opening area of the distributed holes 4 a per unit area of the partition plate 4, and the embodiment is advantageous for decreasing the number of parts to achieve a reduction in cost.

Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. 

1. A combustion apparatus, comprising: a combustion housing; a partition plate provided in the combustion housing to partition a space in the combustion housing into a combustion chamber and an air supply chamber on a lower side of the combustion chamber; a plurality of rich-lean burners arranged in a right-left direction of the combustion chamber, each of the rich-lean burners including a burner main body elongated in a front-rear direction thereof, a lean flame port jetting out a lean mixture gas of a fuel concentration leaner than a theoretical air fuel ratio, and a couple of rich flame ports situated on both sides of the lean flame port in a right-left direction thereof to jet out a rich mixture gas of a fuel concentration richer than that of the lean mixture gas, the lean flame port and the rich flame ports situated at an upper end of the burner main body; a multiplicity of distributed holes formed in the partition plate through which distributed holes secondary air is supplied from the air supply chamber to the combustion chamber; a flame rod facing to an upper side of a part of the rich-lean burners to stop combustion when the flame rod does not detect any flames owing to a flame lift at a time of an oxygen deficiency, wherein a supply quantity of the secondary air to the part of the rich-lean burners to which part the flame rod faces is larger than those to other parts.
 2. The combustion apparatus according to claim 1, wherein the distributed holes in a part of the partition plate through which part the secondary air to flow to the part of the rich-lean burners to which part the flame rod faces passes are formed to have an opening area of the distributed holes per unit area of the partition plate larger than those of other parts. 